This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 199 06 126.2, filed on Feb. 13, 1999, the entire disclosure of which is incorporated herein by reference.
The invention relates to a method and an apparatus for loosening and removing a tightly connected bolt arrangement that secures two structural components together, for example, the structural surface panels of an aircraft.
It is common in the field of aircraft construction, and also in the construction of other vehicles and various structural assemblies, to use connection bolts to connect or secure together plural structural components with each other. For example, the surface structural components such as fuselage panels of an aircraft are typically connected together by such connection bolt arrangements. Each connection bolt arrangement includes a connection bolt or stud arranged within an expansion sleeve. This connection bolt arrangement passes through a bored hole in the two structural components that are to be connected together. Due to a wedge-shaped or conical configuration of the exterior of the connection bolt and the interior of the expansion sleeve, a tight wedging or clamping effect between the connection bolt and the expansion sleeve, and between the expansion sleeve and the two structural components, is achieved when the connection bolt is driven into the expansion sleeve.
Thereby, the wedging effect causes the connection bolt to be tightly held in the expansion sleeve in a force-locking or pressure-locking manner. The terms xe2x80x9cforce-lockingxe2x80x9d or xe2x80x9cpressure-lockingxe2x80x9d herein relate to a frictional contact and connection that does not involve a positive form-locking connection. Furthermore, the connection bolt may be threaded or otherwise configured to provide an additional degree of connection between the connection bolt and the expansion sleeve. The term xe2x80x9cboltxe2x80x9d throughout this specification is not limited to a threaded bolt, but instead also encompasses an unthreaded bolt or stud or pin.
Once the above described type of connection is established, it is considered to be a substantially permanent connection. Nonetheless, occasionally such connections need to be loosened and removed in order to disassemble the two connected structural components, for example if an assembly error or defect has been discovered. A tool known as a so-called xe2x80x9cbig Cxe2x80x9d in the field of aircraft construction has traditionally been used for releasing such expansion bolt connections of mutually secured surface panels of an aircraft. Such a tool is particularly exemplified by tool No. 98 D 55307530 sold by DLH Frankfurt, Federal Republic of Germany. This tool generally consists of a C-shaped planar body with a hand-operated spindle drive mechanism, and generally operates according to the principle of a C-shaped screw clamp or C-clamp. This tool releases the above described bolt connection solely by applying a compression force against the expansion sleeve and the connection bolt that is force-locked therein, whereby this compression force is applied by the threaded spindle of the tool in the axial direction of the spindle. The required compression force is generated solely by a rotational moment or torque that is manually applied to the spindle mechanism. This is disadvantageous in view of the very high applied compression forces that are necessary for releasing such bolt connections.
A further disadvantage is that the tool is relatively large, cumbersome, and heavy, and cannot be disassembled into individual parts for transport and storage, whereby these parts can then be reassembled to form the complete tool at the worksite for example. Thus, the known tool must always be transported, stored, handled, and used at its final utilization location in its complete cumbersome configuration. Due to the high weight and large size of the tool, it is necessary to use great care in preparing the disassembly site at which the bolt connection is to be removed, and several people are required for handling the tool and mounting it at the work location. A single person is barely or not at all able to handle the so-called xe2x80x9cbig Cxe2x80x9d, and even then only with great physical effort. In practice, it is often the case that several attempts of applying the compressive force to the bolt connection are necessary for ultimately releasing the bolt, whereupon the bolt then suddenly is released in a sudden impact or jump-like manner. It is thus not possible to avoid the situation that the large heavy tool falls down when the connection is suddenly released, whereupon injuries to the workers and damage of the structural components can arise.
A further shortcoming of the known tool is that the spindle drive mechanism suffers great wear due to the extreme compression loads that must be applied to the bolt connection each time such a connection is to be released. Since the entire required release force must be generated by the rotation of the spindle drive, the spindle threading and the like are subjected to wear.
The technological background in the present context of removing such bolt connections is also exemplified by the disclosures of U. S. Pat. No. 3,237,291, and German Patent Publications DE-AS 1 300 471, DE 198 03 732 A1, and DE 44 34 152. While these patent publications disclose the general background or state of the art in this field, they do not disclose a tool and a method for removing connection bolts of the above described kind, which are able to overcome the above mentioned disadvantages of the prior art.
In view of the above, it is an object of the invention to provide a method and an apparatus for loosening and removing, or generally releasing, connection bolt arrangements that mechanically secure two or more structural components to each other. More particularly, it is an object of the invention to provide such an apparatus and a method, whereby the required forces are not entirely manually applied, and particularly are not entirely applied by a single torque applied to a single rotatable spindle. The invention further aims to minimize the likelihood of damage being caused to the structural components during the operation of mounting the apparatus, releasing the bolt connection, and then de-mounting the apparatus from the structural components. The degree of wear of the parts of the apparatus is to be reduced. The effort involved in releasing such bolt connections as well as the danger of injuries and the like are to be reduced or minimized through the invention, while also making the apparatus more easily handleable, storable, and transportable. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as are apparent from the present specification.
The above objects have been achieved in an apparatus or tool for releasing a connection bolt arrangement that includes a connection bolt fitted into an expansion sleeve, and that mechanically secures together at least two structural components. The apparatus includes two levers that are pivotally connected to each other, and a stamping actuator arranged between the two levers to apply a stamping force to the levers and thereby cause the levers to pivot relative to each other about the pivot joint connecting the two levers.
A first one of the levers has an opening or recess therein, with dimensions adapted to the outer dimension of a protruding end of the expansion sleeve, and to the outer dimension of an end of the connection bolt received in the protruding end of the expansion sleeve, so that the end surface of the expansion bolt is received in the recess and rests against a support shoulder thereof, while the connection bolt can freely move into the opening at the center of the recess in the first lever. The second lever has a pressing block that is configured and adapted to receive and press against a bolt head end or narrower tapered end of the connection bolt without pressing against the expansion sleeve. Thereby, a force applied by the stamping actuator is transferred through the two levers to apply respective pressing forces to the connection bolt and the expansion sleeve in such opposite directions and in such a manner to tend to push the connection bolt out of the expansion sleeve and thereby release the bolt from the sleeve.
Furthermore, a pulling extraction device is mounted on the first lever so as to engage the larger-diameter end of the connection bolt and apply a pulling or tension force to the connection bolt relative to the first lever, whereby this pulling force further tends to pull the connection bolt out of the expansion sleeve. The combination of the pulling force and the pushing forces applied to the connection bolt arrangement release the frictional or force-locked engagement of the bolt in the expansion sleeve, and move the bolt at least partially out of the sleeve. Thereafter, the tool is removed from the connection bolt arrangement and the released bolt arrangement can be removed from the structural components that it was securing.
The above objects have further been achieved according to the invention in a method of releasing a connection bolt arrangement including a connection bolt fitted into an expansion sleeve. This method is carried out using a tool that has two levers pivotally connected to each other and a pulling extraction device mounted on one of the levers. According to this method, the levers are pivoted relative to each other about a pivot joint so that the first lever pushes against the expansion sleeve in a first direction, while the second lever pushes against the connection bolt in a second direction opposite the first direction. Thus, the pushing forces applied by the first and second levers to the connection bolt arrangement have a tendency, or are applied in a direction, to push the connection bolt out of the expansion sleeve. Moreover, the method further includes applying a pulling tension force to a first end of the bolt relative to the first lever using the pulling extraction device, This pulling force tends to pull the connection bolt out of the expansion sleeve. The combination of the pushing forces applied by the levers and the pulling force applied by the pulling extraction device finally releases the connection bolt from the expansion sleeve, so that the bolt and sleeve may be removed from the structural components that were being mechanically connected by the connection bolt arrangement.